1. 1A-0 Definition: a comparative advantage exists when one party can produce a good or service at a lower opportunity cost than another party. The Theory of Comparative Advantage

2. 1A-1 The Geometry of Comparative Advantage Consider the example given in appendix 1A. There are two countries, A and B, who can each produce only food and textiles. Initially they do not trade with one another.

3. 1A-2 The Geometry of Comparative Advantage 300 Food Textiles 180 A production possibilities curve shows the various amounts of food or textiles that each country can make. The production possibilities of country A are such that if they concentrated 100% of their resources into the production of textiles, they could produce 180 million yards of textiles. If country A chose to concentrate 100% of their resources into the production of food, they could produce as much as 300 million pounds of food. Country A can produce any combination of food and textiles between these two points.

4. 1A-3 The Geometry of Comparative Advantage 300 Food Textiles 180 60 200 As a practical matter, the citizens of country A must choose a point along their production possibilities curve; initially they choose 200 million pounds of food, and 60 million yards of textiles.

5. 1A-4 The Geometry of Comparative Advantage 1,200300 Food Textiles 180 900 240 60 200 The production possibilities of country B are such that if they concentrated 100% of their resources into the production of textiles, they could produce 240 million yards of textiles. If country B chose to concentrate 100% of their resources into the production of food, they could produce as much as 900 million pounds of food.

6. 1A-5 The Geometry of Comparative Advantage 1,200300 Food Textiles 180 900 240 60 200 600 As a practical matter, the citizens of country B must choose a point along their production possibilities curve; initially they choose 600 million pounds of food, and 80 million yards of textiles. 80

7. 1A-6 The Geometry of Comparative Advantage 300 Food Textiles 180 900 240 60 200600 80 Country A enjoys a comparative advantage in textiles because they have to give up food at a lower rate than B when making textiles. Put another way, country B enjoys a comparative advantage in food because they have to give up textiles at a lower rate than A when making more food. Geometrically, a comparative advantage exists because the slopes of the production possibilities differ.

8. 1A-7 The Geometry of Comparative Advantage 300 Food Textiles 180 900 240 60 200600 80 If the countries specialize according to their comparative advantage, then country A should make textiles and trade for food, while country B should grow food and trade for textiles.

9. 1A-8 The Geometry of Comparative Advantage 1,200 300 Food Textiles 420 180 900 240 60 200600 80 Before trade, if both countries made only textiles, the combined production would be 420 million yards of textiles = 240 + 180. Before trade, if both countries made only food, the combined production would be 1,200 million pounds of food = 900 + 300.

10. 1A-9 The Geometry of Comparative Advantage 1,200300 Food Textiles 420 180 900 240 60 200600 80 The combined production possibilities curve of country A and B without trade are shown in the green line.

11. 1A-10 The Geometry of Comparative Advantage 1,200300 Food Textiles 420 800 180 900 240 60 200600 80 Before trade, the combined production is 800 million lbs of food and 140 million yards of textiles. 140

12. 1A-11 The Geometry of Comparative Advantage 1,200300 Food Textiles 420 800 140 900 240 60 200600 80 County B can produce food at a lower opportunity cost, so let B produce the first 900 million pounds of food. Country A can produce textiles at a lower opportunity cost, so let them produce the first 180 million yards of textiles. 180

13. 1A-12 The Geometry of Comparative Advantage 1,200300 Food Textiles 420 800 140 180 900 240 60 200600 80 The combined production possibilities curve with trade is composed of the original curves joined as shown.

14. 1A-13 The Geometry of Comparative Advantage 1,200300 Food Textiles 420 800 140 180 900 240 60 200600 80 The gains from trade are shown by the increase in consumption available—an extra 100 million pounds of food and 40 million yards of textiles are now available in excess of the pre-trade consumption.